1. Field of the Invention
This invention relates to a weft insertion controlling method for a shuttleless weaving machine which can cope appropriately with a variation in weft insertion condition when weft insertion is performed using a drum-type length measuring reserving apparatus in an arbitrary weft insertion pattern, for example in 2.times.2 weft insertion pattern or in 2.times.1 weft insertion pattern.
2. Discussion of the Background
Technique of performing the above mentioned multi-color weft insertion on a shuttleless weaving machine using a drum-type length measuring reserving apparatus (hereinafter referred to merely as length measuring apparatus) is known, for example, by Japanese Patent Publication Application No. 61-27500.
According to the technique, length measuring apparatus are used which include a drum, a positive yarn supply mechanism such as a delivery roller for supplying a yarn to the drum at the same yarn speed as a circumferential speed of the drum, and a restraining pin adapted to be engaged with or disengaged from a yarn on the drum to control an amount of the yarn reserved on the drum. In particular, while each of the weft yarns is continuously fed to its corresponding drum at regular speed, a repeat of a weaving cycle or cycles wherein a certain weft yarn is inserted into a warp shed (hereinafter referred to as weft insertion cycle) and another weaving cycle or cycles wherein another weft yarn is inserted (hereinafter referred to as weft non-insertion cycle) is performed to realize multi-color weft inserting operation in accordance with a predetermined weft insertion pattern.
A weft inserting operation in such a weft insertion cycle as mentioned above is performed using a weft inserting member such as a weft inserting nozzle and includes a combination of (1) a free flying condition wherein a yarn reserved on the drum is weft inserted while being unwound freely from the drum and (2) a restrained flying condition wherein a yarn is inserted at such a speed that the positive yarn supply mechanism feeds a yarn to the drum without changing the reserved amount of the yarn on the drum. The latter is performed by engaging the restraining pin with a yarn on the drum to prevent the yarn from being unwound freely from the drum or by reducing the reserved amount of a yarn on the drum completely to zero and supplying a yarn directly from the positive yarn supply mechanism to the weft inserting member. It is to be noted that it is known that a dispersion of lengths of a weft inserted for various weft insertion cycles (each such length will be hereinafter referred to as one-pick length) can be minimized by setting a restrained flying condition to a section near an end point of each weft insertion cycle.
A 2.times.2 weft insertion pattern will be examined here wherein, as shown in FIG. 12, four weaving cycles are set as one repeat and two former weaving cycles are determined as weft non-insertion cycles while two latter weaving cycles are determined as weft insertion cycles.
If the one-pick length which is a unit defined by a circumferential length of the drum is .sub..DELTA. n which is equal to .sub..DELTA. n=6.5 (turns), then the drum must be driven at an equal speed so that a yarn of 2.sub..DELTA. n-13.0 (turns) may be reserved for one repeat. Since the former two weaving cycles are set as weft non-insertion cycles, the reserved amount N of a yarn on the drum increases linearly at a rate of 13/4=3.25 (turns/weaving cycle). Then, if a weft insertion section T is entered during the first weft insertion cycle (the third weaving cycle in the one repeat), then the reserved amount N decreases suddenly for a free flying condition section T1. Then in a restrained flying condition section T2, the reserved amount N does not vary while weft insertion is performed at a yarn speed which depends upon the circumferential speed of the drum. Thus, at the end point of the weft insertion section T, that is, at an end point of the weft insertion cycle, weft insertion of the predetermined one-pick length .sub..DELTA. n=6.5 (turns) comes to an end. A quite similar weft inserting operation is performed also in a succeeding weft insertion cycle (the fourth weaving cycle).
Here, the reserved amounts n1 and n0 at the end points of the weft insertion cycles are n1=3.25 (turns) and n0=0 (turn), respectively. Accordingly, at the end point of the first weft insertion cycle, an imaginary reserved amount N1 when it is presumed otherwise that weft insertion is not performed is provided by N1=13.times.3/4=9.75 (turns), and EQU n1=N1-.sub..DELTA. n=9.75-6.5=3.25 (turns)
stands. On the other hand, at the end point of the last weft insertion cycle (the fourth weaving cycle in the one repeat), an imaginary reserved amount M0 when weft insertion only in the last weft insertion cycle is not performed is provided by M0=N0-.sub..DELTA. n=13-6.5=6.5 turns, and EQU n0=M0-.sub..DELTA. n=6.5-6.5=0 (turn)
stands where N0 is an imaginary reserved amount at the end point of the last weft insertion cycle when weft insertion is performed i.multidot.n neither of the two weft insertion cycles. After then, the predetermined weft insertion pattern is performed repetitively while driving the drum at the equal speed in a similar as described above.
It is to be noted that, in order to allow restrained flying in a condition wherein the reserved amount of a yarn on the drum is kept equal to N=n1=3.25 (turns), a restraining pin P is disposed at a location displaced by a distance equal to one fourth the circumferential length of the drum D in a circumferential direction from a point A of the drum D to which a yarn W is supplied as shown in FIG. 13(A), and a remaining amount n1=3.25 (turns) on the drum D should be realized. It is to be noted that a pair of delivery rollers R on the upstream side of the drum D are provided to supply a yarn W positively toward the drum D at a yarn speed equal to a circumferential speed of the drum D, and a pair of yarn guides G1 and G2 are disposed forwardly and rearwardly of the drum D. It is also to be noted that, in restrained flying of N=n1=0 (turn), a yarn W should be forwarded only by way of the delivery rollers R and the yarn guides G1 and G2 irrespectively of the drum D and the restraining pin P as shown in FIG. 13(B).
With such conventional technique as described above, if the weft insertion conditions such as a one-pick length for each weft insertion cycle and a number of weft insertion cycles in one repeat are varied, then the location of the restraining pin must necessarily be changed in a circumferential direction of the drum. Accordingly, in the conventional technique, the operation in working is very complicated.
For example, referring to FIG. 12, if the one-pick length .sub..DELTA. n is changed from .sub..DELTA. n=6.5 to .sub..DELTA. n=7.5 (turns), then N0, N1, and n1 would be changed as follows: EQU N0=2.times.7.5=15.0 EQU N1=15.times.3/4=11.25 EQU n1=11.25-7.5=3.75
Accordingly, restrained flying at the end point of the first weft insertion cycle must involve a remaining amount of n1=3.75 (turns) on the drum, and to this end, the restraining pin P must necessarily be moved 180.degree. from that shown in FIG. 13(A) to dispose the same at a location displaced by a distance equal to three fourths, rather than one fourth the circumferential length of the drum D in a circumferential direction from the point A at which the yarn W is supplied.